| Liusha Bay is located in the southwest of Guangdong Leizhou peninsula, with about900 square hectares of seagrass bed, and the dominant species is Halophila ovalis, which is listed as one of the national major research and protection project. Halophila ovalis is subtropical, perennial and widely distributed submerged plant, which is usually formed large seagrass bed with other seaweed. The seagrass bed has great potential value in ecosystem services and plays an extremely important role in adjusting the balance of marine ecosystems. In recent years, due to the human’s disorder development activities and natural factors, causing the epiphyte blooming whit the eutrophication of ocean was increasingly severe. And in turn, it will affect the growth and reproduction of seagrass, and a recession phenomenon of widespread is appeared. So, this article selects Halophila ovalis as the research object, through carried out anniversary investigation and environmental simulation test, to study the anniversary changing of epiphyte algae, and further discusses the implantation effects to the growth and physiological and biochemical characteristics of seagrass. The main results are as follows:1. In total, 61 species 15 genus of epiphyte algae were identified(including form and variants), these are affiliated to bacillariophyta, and within the samples, great priority belongs to Nitzschia, Navicula and Amphora, the proportion of the species were 15%, 13%and 10%, respectively. The cell density of epiphyte algae showed a temporal and spatial variation. The cell density presented obviously seasonal variation in time, and the basic trend in order was spring, winter, summer and autumn. On the space, cell density of epiphyte algae at different coastal zone showed significant difference(P<0.05), and the cell density significantly changed with seasons, ranged from 3.96×103ind·cm-2 ~49.33×103 ind·cm-2, in turn were far coastal zone, middle coastal zone and near coastal zone. 11 dominant species were identified. In the spring, G. oceanica was the dominant specie and the dominance was 0.22; in the winter, L. flabellata was the dominant specie and the dominance was 0.21; C. Scutellum was the dominant specie both in summer and autumn,the dominance were 0.18 and 0.19, respectively. The most common were C. scutellum, N.marina and M. brauni as dominant species throughout the year. In all seasons, the Shannon diversity index and evenness ranged from 0.414 to 0.506 and 2.398 to 3.009, respectively.It is indicated that the water in Liusha Bay was light or moderate polluted.2. The epiphyte biomass and chlorophyll a content showed distinctly seasonal variation. In the fall, these indexes both achieved to minimum, to 0.098 mg/g and 0.015mg/g, respectively, and then as followed were winter and summer. During the spring, the content were up to maximum, 0.605 mg/g and 0.118 mg/g, respectively. The epiphyte biomass and chlorophyll a content at different coastal zone showed significantly difference(P<0.05), which in order were far coastal zone, middle coastal zone and near coastal zone.3. The inhibition rate of epiphyte on the photosynthesis rate of Halophila ovalis showed distinctly seasonal variation. The inhibition rate reached maximum up to 50.72%in the spring, and as followed were winter and summer, to 47.13% and 37.15%,respectively. The inhibition rate achieved to the minimum in autumn, which was 30.61%.Beyond that, there was a significantly positive correlation between the epiphytes biomass and inhibition rate, did as chlorophyll a content.4. The epiphyte has great effects on the content of soluble protein and pigment of Halophila ovalis(P<0.05). The soluble protein content was changing with time and showed firstly increases and then decreases. The chlorophyll a, chlorophyll b, carotenoids and total pigment content all presented a sustained downward trend during the training. These contents in the group with epiphyte in treatment were all lower than the control group.5. The epiphyte has great effects on the enzyme activity of CAT of Halophila ovalis(P<0.05). And the enzyme activity of CAT in ground part was higher than the underground part. The activity of CAT in the group with epiphyte in treatment were lower than the control group, and showed firstly decreases and then increases, reached up to 16.579U/(mg·min) at the end of test, which was 1.76 times of the group with epiphyte. The groups in the underground part were presented firstly increases and then decreases, and the control group was 1.57 times of the group with epiphytes.The epiphyte has great effects on the enzyme activity of POD of Halophila ovalis(P<0.05). The groups in the ground part were presented sustained downward trend. At the end of the test, the activity of POD in the group without epiphyte was 42.249 U/(mg·min),which was 1.23 times of group with epiphytes. However, the POD of underground part increased slowly, and reached the peak at the third week, the activity of POD in the group without epiphytes was 1.99 times of group with epiphytes.1. The epiphyte has great effects on the enzyme activity of SOD of Halophila ovalis(P<0.05). At the begin of test, the SOD of the group without epiphyte in ground part was95.097 U/mgprot, which was 1.43 times of group with epiphyte. And the SOD of the group without epiphyte in underground part was 48.865 U/mgprot, which was 1.56 times of group with epiphyte. The activity of SOD persistently decreased.2. The epiphyte has great effects on the content of MDA of Halophila ovalis(P<0.05). The content presented a sustained increased trend and reached a peak at the end of test. The MDA content of group with epiphyte was 1.49 times of the control group in the ground part; the content of group with epiphyte was 1.71 times of the control group in the underground part. |
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